Wheel bearing apparatus is generally known that can support a wheel of a vehicle relative to a suspension apparatus. Also, it incorporates a wheel speed detecting apparatus to detect a rotation speed of a wheel of the vehicle to control an anti-lock braking system (ABS). Such a bearing apparatus generally includes a wheel speed detecting apparatus with a magnetic encoder. The encoder has alternately magnetic poles arranged along its circumference. It is integrated into a sealing apparatus arranged between inner and outer members to contain the rolling elements (balls) between the members. It also includes a wheel speed detecting sensor to detect the variation in the magnetic poles of the magnetic encoder according to the rotation of the wheel.
The wheel speed sensor is usually mounted on a knuckle after the wheel bearing apparatus is mounted on the knuckle, which forms a portion of a suspension apparatus. Wheel bearing apparatus incorporating a wheel speed detecting apparatus has been proposed. Here, a wheel speed detecting sensor is incorporated in the wheel bearing in order to reduce the size of the wheel bearing apparatus as well as to eliminate the troublesome air gap adjustment between the wheel speed sensor and the magnetic encoder.
A wheel bearing apparatus incorporating a wheel speed detecting apparatus is shown in FIG. 6. The wheel speed detecting apparatus includes a magnetic encoder 51 fit onto an inner ring 50. An annular sensor holder 53 is mounted on the end of an outer member 52 opposite to the magnetic encoder 51. A wheel speed sensor 54 is mounted on the sensor holder 53 and arranged opposite to the magnetic encoder 51, via a predetermined air gap. The encoder 51 is adhered on one side of a slinger 57 forming a seal 56.
The seal 56 includes a slinger 57, formed with an L-shaped cross-section, and an annular sealing plate 58. The sealing plate 58 is also formed with an L-shaped cross-section. The plate 58 is mounted on the outer member 52 opposite to the slinger 57. The slinger 57 has a cylindrical portion 57a fit onto the inner ring 50. A standing portion 57b radially extends outwardly from the cylindrical portion 57a. On the other hand, the sealing plate 58 includes a metal core 59 fit into the end of the outer member 52. A sealing member 60 is integrally bonded to the metal core 59, via vulcanized adhesion. The sealing member 60 is formed of an elastomer, such as rubber, and includes a side lip 60a in sliding-contact with the standing portion 57b of the slinger 57. A grease lip 60b and a middle lip 60c are both in sliding-contact with the cylindrical portion 57a of the slinger 57.
The sensor holder 53 includes a cover 55 formed of a steel plate. The cover 55 is adapted to fit onto an outer member 52. A holding portion 61 is formed of synthetic resin and is joined to the bottom portion 55c of the cover 55. The wheel speed sensor 54 is embedded in the holding portion 61. The cover 55 includes a cylindrical fitting portion 55a, a flange portion 55b, and the bottom portion 55c. The flange portion 55b extends radially inward from the fitting portion 55a. The bottom portion 55c axially extends from the flange portion 55b. 
The output of the wheel speed sensor 54 is sent to a controller (not shown) of the ABS, via a harness 62. The harness 62 is connected to a take-out port 63 mounted on the holding portion 61. The take-out port 63 is formed at an inclined angle α set larger than an inclined angle β of the outer circumference of an outer joint member 64.
Accordingly, it is possible to prevent hanging down of the harness 62 and thus interference of the harness 62 with the outer joint member 64. Thus, it is possible to reduce the number of clips to a minimum to secure the harness 62. In addition, it is unnecessary to excessively bend the harness 62 itself. Thus, it is possible to further improve the reliability of the harness 62 while preventing the generation of bad influences on the electric wires within the harness 62. Accordingly, it is possible to simplify the securing operation of the harness 62 and thus to reduce the manufacturing cost of the apparatus. (Reference Patent Document 1: Japanese Laid-open Patent Publication No. 145418/2006)
However, problems exist with the prior art wheel bearing apparatus incorporating a wheel speed detecting apparatus. The accuracy of detection is detracted if muddy water, including salt or magnetic powder, enters into the detecting portion between the encoder 51 and the wheel speed sensor 54.
In addition if the cover 55 becomes corroded by salty water, the securing force of the cover 55 relative to the outer member 52 is diminished. Thus, the cover 55 is enabled to move axially. This not only causes reduction of the detecting accuracy but fixing of the cover 55 and the outer member 52 caused by rust propagation between the two. Thus, a servicing operation to replace the parts forming the bearing apparatus would be difficult.